OAuth2 (#32)

* make auth method asyncs

* oauth2 demo support

* full coverage

* update docs

tests/testresources/core/ahriman.ini

@@ -10,6 +10,10 @@ root = /
 
 [auth]
 allow_read_only = no
+client_id = client_id
+client_secret = client_secret
+oauth_provider = GoogleClient
+oauth_scopes = https://www.googleapis.com/auth/userinfo.email
 salt = salt
 
 [build]